Motor speed controls for D.C. motors have been long used in a variety of applications. Such speed controls, while providing the ability to vary the motor speed, are generally designed to operate a D.C. motor unidirectionally. Indeed, if reversing is attempted with a standard speed control by instantly applying a voltage to the motor of the opposite polarity, arcing and eventual destruction of motor and controller will result due to the counter-EMF generated by the operating motor.
Circuits designed to permit reversing of a D.C. motor without causing damage are known in the prior art. Such circuits generally operate a set of relay contacts to apply a reversing voltage to the motor and to prevent damage, mechanical interlocks or electrical sensing circuits are used to inhibit application of the reversing voltage until the motor has come to a complete stop and/or the counter-EMF has decreased to essentially zero. However, although such circuits are known they are generally complicated and expensive and thus find few applications for small size D.C. motors.
It is, therefore, an object of the instant invention to provide a circuit capable of reversing a D.C. motor, which circuit is relatively inexpensive, easy to manufacture and highly reliable.
It is a further and general object of the instant invention to provide an anti-plug reversing circuit that is relatively simple and uncomplicated, yet capable of wide use with low cost D.C. motors.